1. Field of the Invention
This invention relates to a disk reproduction device that performs a reproduction of a digital versatile disk (DVD), etc.
2. Related Art
Recently, people's interests are focusing on the DVD as a recording medium of a disk type. The DVD has a diameter of 12 cm, and a thickness of 1.2 mm. Having the same dimensions as the compact disk (CD), the DVD has increased the recording density to reach 4.7 GB by the single layer, and 8.5 GB by the double layer.
By adopting the image data compression technique and audio data compression technique according to the MPEG2, the DVD accommodates various types of data mixed therein. Considering the case in which a movie is recorded in the DVD, normally video data and audio data are recorded. However, the storage of the caption data of plural languages other than these data, for example, will make it possible to display the caption of a language that a user selects. Also, the storage of the static images of profiles of movie directors, actors, actresses, and the like will make it possible to display these contents by the user's operation. Further, photographing a single object in plural directions or separately photographing plural objects, with video data taken in plural photographing directions (maximum, 9 angles), will achieve a multi-angle function whereby the user is able to reproduce the video data in accordance with the angle selected by the user. Also the storage of the video data and audio data corresponding to plural stories will achieve a multi-story function whereby the user is able to develop a story in accordance with the user's selection. The DVD reproduction device reproduces the DVD that holds such various data.
FIG. 15 illustrates a partial construction of a conventional DVD reproduction device, until the point data read from a DVD is inputted to the decoder. As shown in the drawing, the conventional DVD reproduction device 500 includes a data read unit 502 that reads data recorded in the DVD, a track buffer 504 that temporarily stores data outputted from the data read unit 502, and a decoder 506 that applies a decoding process to data outputted from the track buffer 504 to reproduce an image.
FIG. 16 illustrates the multi-angle function executed by the DVD reproduction device shown in FIG. 15. For example, in blocks 2-4 are recorded images by plural angles, and the user is able to select an arbitrary angle. In order to achieve this type of multi-angle function, the DVD has data by a unit of each block recorded, whereby the data of an arbitrary angle instructed by the user is selectively read, and the reproduction corresponding to the angle is executed. For example, when the user selects the angle 3 in the reproduction corresponding to the blocks 2-4 shown in FIG. 16, the data read unit 502 selectively reads only the data of the angle 3 among the blocks 2-4, as shown in FIG. 17, which are stored in the track buffer 504. Thereafter, the data of the angle 3 stored in the track buffer 504 are read out in the order stored therein, and the decoder 506 reproduces the image, etc., corresponding to the angle 3.
In the DVD-video standard, in order that a reproduced image does not become intermittent even in the course of the angle switching, the storage capacity of the track buffer 504, for example, is stipulated as 4M bits, the transfer rate between the data read unit 502 and the track buffer 504 is stipulated as 11.08M bits/sec, and the transfer rate between the track buffer 504 and the decoder 506 is 10.08M bits/sec (maximum, 8M bits/sec in transferring ILVU).
As mentioned above, the provision of the track buffer 504 with the DVD reproduction device 500 is effective to prevent the image from becoming intermittent. However, during the angle being switched, there occurs a time difference between a timing of the angle switching instructed by the user and a timing of the angle being actually switched, which gives the user a feeling that something is wrong.
As shown in FIG. 18, it is assumed that, while data of the block 2 is read from the track buffer 504 and the decoder 506 is executing the reproduction corresponding to the angle 3, data corresponding to the angle 3 in the block 3 is looked ahead and already stored in the track buffer 504. At this timing, if the user selects the angle 1 and instructs the angle switching, the data read unit 502 will change the data readout position and start to read the data corresponding to the angle 1. Therefore, the data corresponding to the angle 3 is used as to the next block, and the actual angle switching is executed after the reproduction operation corresponding to the further next block 4. In other words, from the user's instruction of the angle switching until the angle switching actually executed in correspondence to the instruction, the reproduction of data for several blocks stored in the track buffer 504 is continued in the state before the angle switching; and accordingly, it takes some time until the start of the reproduction after the instructed angle switching.
The present invention has been made in view of the above problem, and it is an object of the invention to provide a disk reproduction device that quickly performs the angle switching in the multi-angle reproduction operation.
In order to solve the foregoing object, in the disk reproduction device of this invention, a data storage means stores the compression data corresponding to each of different plural angles of the image with one reproduction timing, and when the angle being a reproduction object is switched, a data reproduction means reads the compression data corresponding to an angle after switching stored in the data storage means to reproduce the image. Therefore, when the angle switching is instructed, the disk reproduction device does not read the compression data of the angle after switching that was newly stored in the data storage means from then on, but uses the compression data of the angle after switching that has already been stored in the data storage means, and thereby executes a reproduction operation corresponding to the angle after switching, thus implementing a swift angle switching in the multi-angle reproduction operation.
Preferably, the foregoing data storage means stores the compression data corresponding to each of the different plural angles in a unit of an interleaved unit, and the data reproduction means switches the compression data being a readout object in a unit of the interleaved unit. To switch the compression data being a readout object in a unit of the interleaved unit enables the seamless reproduction that does not make a reproduction image intermittent, and also enables a swift and natural angle switching.
Also, it is preferable to store the compression data corresponding to each of the different plural angles in the data storage means, only when a data transfer rate at which the compression data read from the disk type recording medium is stored in the data storage means is greater than a value obtained by multiplying the number of the plural angles and a readout bit rate at which the data is read from the data storage means. When the speed to read the compression data from the disk type recording medium is lower, or on the contrary, when the speed to read the compression data from the data storage means is higher, or when the number of the angles is multiple, it can be avoided that the writing of the compression data into the data storage means is not in time to become under flow, whereby a natural reproduction image without intermission can be achieved. Further, in the disk reproduction device of the invention, after the data storage means selectively stores the compression data corresponding to each of the different plural angles of the image with one reproduction timing, when the angle being a reproduction object is switched, a re-read instruction means instructs the signal processing means to read the compression data corresponding to an angle after switching, of which reproduction timing is the same as that of the compression data corresponding to the angle before switching already read and stored, and a data replacement means replaces the compression data read in accordance with the instruction. Therefore, when the angle switching is instructed, the disk reproduction device does not read the compression data of the angle after switching that was newly stored in the data storage means from then on, but newly reads the compression data of the angle before switching already stored in the data storage means and the compression data of the angle after switching, of which reproduction timing is the same, and thereby executes a reproduction operation corresponding to the angle after switching, thus implementing a swift angle switching in the multi-angle reproduction operation.
Preferably, the foregoing data storage means stores the compression data corresponding to each of the different plural angles in a unit of an interleaved unit, and the data reproduction means switches the compression data being a readout object in a unit of the interleaved unit. To switch the compression data being a readout object in a unit of the interleaved unit enables the seamless reproduction that does not make a reproduction image intermittent, and also enables a swift and natural angle switching.
Also, it is preferable, when storing the compression data corresponding to any one of the angles in the data storage means, to generate angle information necessary for reading the compression data corresponding to the other angles with the same reproduction timing, and to store the angle information in association with the compression data in the data storage means.
Also, preferably the re-read instruction means designates a read position of the compression data corresponding to the angle after switching, so that a replacement of the compression data corresponding to the angle before switching with the compression data corresponding to the angle after switching does not make a reproduction image intermittent. Depending on the quantity of the compression data being a reproduction object at the moment of the angle switching being instructed, or the quantity of the compression data being next read, the replacement of the compression data cannot be made in time occasionally, and in consequence, the reproduction image becomes intermittent. By setting the read position of the compression data to avoid such inconveniences, it becomes possible to prevent unnatural reproduction images from being displayed, and to reduce an unpleasant feeling and a feeling that something is wrong when the user views the reproduction image.